JP3857394B2 - Fixing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fixing device including a fixing roller and a pressure roller.
[0002]
[Prior art]
Conventionally, a typical fixing device of this type has a fixing roller having a heat source and a pressure roller pressed against the fixing roller, and the pressing force of the pressure roller is switched to a plurality of types. The thing which has the temperature detection member which detects the surface temperature of this can be mention | raise | lifted.
[0003]
In such a case, if the amount of heat applied to the transfer paper is too large, hot offset occurs. On the other hand, if the amount is too small, cold offset and fixing property are deteriorated. By the way, the optimum heat quantity differs depending on the difference in the width of the nip portion between the fixing roller that pressurizes the transfer paper and the pressure roller and the type of the transfer paper.
[0004]
[Problems to be solved by the invention]
In order to cope with such a situation, there is one disclosed in Japanese Patent Laid-Open No. 2-148077. However, this is to adjust the pressing force of the pressure roller in response to the difference in the thickness of the transfer paper, and to cope with the difference in the nip width between the fixing roller and the pressure roller. There is a problem that can not be.
[0005]
Therefore, the object of the present invention is to solve the problems of the conventional fixing device as described above, and to accurately correspond to the difference in the width of the nip portion between the fixing roller and the pressure roller and the difference in the type of transfer paper, An object of the present invention is to provide a fixing device that can optimize the amount of heat applied to transfer paper and improve the fixing quality.
[0006]
[Means for Solving the Problems]
In order to achieve the above-described object, the present invention has a fixing roller having a heat source and a pressure roller pressed against the fixing roller, and the pressing force of the pressure roller is switched to a plurality of types and fixing is performed. In the fixing device having a temperature detecting member for detecting the surface temperature of the roller, the invention according to claim 1 is a low-pressure mode in which a nip width between the fixing roller and the pressure roller is small, and a nip between the fixing roller and the pressure roller. width is large and the high-pressure mode is set, and an intermediate nip width between the nip width _{X H} when the nip width _{X L} and the high pressure mode when the low-pressure mode _{X M (X M = (X} L + X H) / 2 ), A temperature gradient A _M (A _M = ΔT _M / Δt) due to a temperature drop ΔT _M for a certain time Δt is set, and the heat source is turned off for a certain time during continuous passage of transfer paper, and the temperature during that time Detection of detection member According based on the temperature change of the surface temperature of the fixing roller by calculating a temperature gradient A in actual sheet feeding, if the temperature gradient A is A <A _M, determines that the low pressure mode, and A ≧ A _M if high mode It is characterized in that there is provided control means for performing control so as to adjust the amount of heat supplied by the heat source so that the amount of heat given to the transfer paper becomes the optimum amount .
[0007]
Similarly, the invention of claim 2 includes a low pressure mode in which the nip width between the fixing roller and the pressure roller is small, and a high pressure mode in which the nip width between the fixing roller and the pressure roller is large, and the nip in the low pressure mode. width _{X L} and the intermediate nip width _X M and the nip width _{X H} when the high pressure mode _{(X M = (X L +} X H) / 2) temperature gradient due to the temperature drop [Delta] T _M for a predetermined time Δt in _a M (a _M = ΔT _M / Δt), and the surface of the fixing roller is detected by detecting the temperature detecting member during a certain period of time while the first transfer sheet passes through the fixing device and the heat source is turned off for a certain period of time. calculating a temperature gradient a during actual sheet passing on the basis of the temperature change, if the temperature gradient a is a <a _M, determines that the low pressure mode, it is determined that a ≧ a _M if the high pressure mode, the transfer sheet So that the amount of heat given to the In which characterized in that a control means for adjusting the supply amount of heat by the source.
[0008]
Similarly, the invention of claim 3 includes a low pressure mode in which the nip width between the fixing roller and the pressure roller is small, and a high pressure mode in which the nip width between the fixing roller and the pressure roller is large, and the nip in the low pressure mode. width _{X L} and the intermediate nip width _X M and the nip width _{X H} when the high pressure mode _{(X M = (X L +} X H) / 2) temperature gradient due to the temperature drop [Delta] T _M for a predetermined time Δt in _a M (a _M = ΔT _M / Δt) is set , and the heat source is turned off for a predetermined time in a state where the temperature of the fixing roller is stable, and based on the temperature change of the surface temperature of the fixing roller by the detection of the temperature detecting member during that time calculating a temperature gradient a in actual sheet passing, if the temperature gradient a is a <a _M, determines that the low pressure mode, it is determined that a ≧ a _M if the high pressure mode, the amount of heat applied to the transfer sheet optimum To the heat source so that the amount In which characterized in that a control means for adjusting the supply amount of heat that.
[0009]
Similarly, the invention described in claim 4 is characterized in that in the invention described in any one of claims 1 to 3, the heat source is turned off non-forcefully.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an image forming apparatus of a copying machine in which an embodiment of the present invention is provided. On a photosensitive member 2 uniformly charged by a first charger 1, a first optical system (not shown) is used. Image exposure 3 is performed to form a negative-positive latent image, and the first developing device 4 develops the first image on the photosensitive member 2 and black toner by contact two-component development.
[0011]
Subsequently, the second charger 13 recharges the photosensitive member 2 including the black toner image portion and the non-image portion, the second image exposure 6 is performed by an optical system (not shown), and again the negative-positive latent potential. An image is formed, and toner having a color tone different from that of the first development is negative-positive developed by the second developing device 5 by non-contact two-component development, and red toner is developed.
[0012]
The black-red two-color image is transferred to a transfer sheet by a transfer belt 9 to which a voltage is applied by a voltage applying means 8 through a bias roller 7 and conveyed. Note that the second developing device 5 is moved between a proximity position and a separation position with respect to the photoreceptor 2 by a solenoid 11 and a spring 12 so as to maintain a minute gap with the photoreceptor 2 only during development. Yes.
[0013]
The conditions for recharging by the second charger 13 in the two-color development are to prevent the development of mixed color of red toner in the black toner development region and to prevent the reverse development of black toner to the red developer, that is, the second developer 5. Is set to be done. Therefore, in the above, a black toner image is formed with a first charging potential of −850 v, a first exposure potential of −100 v, and a first developing bias of −550 v. The second charging potential is obtained by an experiment to satisfy the above condition, and the second charging grid potential is applied at -900v so that the black toner image portion recharging potential is -800 to -900v. The second developing device 5 forms a red toner image with a second exposure potential of −100v and a second developing bias of −750v.
[0014]
In the image forming apparatus as described above, when the black, red, black, or red simultaneous two-color mode is selected by the operation unit (not shown), the black developer or the red developer is operated correspondingly, Black toner and red toner are transferred to the transfer paper 10, and the transfer paper 10 carrying the black toner or red toner is conveyed to the fixing device of the present invention, where the image is fixed.
[0015]
FIG. 2 shows an embodiment of a fixing device according to the present invention. The surface of a fixing roller 21 is coated with a heat-resistant release material such as PFA or PTFE, and a heat source 22 comprising a halogen heater or an infrared heater is provided inside. Is provided. The fixing roller 21 is heated by the heat source 22, the temperature of the fixing roller 21 is detected by the temperature detecting means 23, and the heat source 22 is controlled so that the temperature of the fixing roller 21 becomes a constant temperature.
[0016]
In this embodiment, reference numeral 24 denotes a pressure roller, the surface of the pressure roller 24 is made of heat-resistant rubber made of silicon rubber, and its support shaft 28 is a vertical plate provided on the side plate 33 via a bearing 25. It is supported by a long groove in the direction so that it can move up and down. The bearing 25 is supported at the base end thereof by a pressure lever 26 supported on the side plate 33 by a pivot 27 so as to be swingable. The free end of the pressure lever 26 is locked to the lower end of the spring 31, and the upper end of the spring 31 is a vertically moving member in which the long hole 30 is slidably fitted to the support pin 29 attached to the side plate 33. Locked to 32. A rotation shaft 34 is rotatably supported on the side plate 33, a gear 35 that meshes with a drive gear (not shown) is attached to the tip, and a cam 36 is attached to the rear thereof. The vertical movement member 32 has a longitudinally long hole (not shown), and the rotation shaft 34 is slidably fitted in the long hole. Is always in contact with the cam.
[0017]
When the rotation shaft 34 is rotated by the operation of the drive gear, the cam 36 is also rotated and displaced, and the lower first pressurizing position (low pressure mode) contacting the lower portion of the cam 36 as shown in FIGS. ) And the upper second pressurizing position (high pressure mode) in contact with the high portion. At the first pressure position, since the tension of the pressure lever 26 by the spring 31 is small, the low pressure mode in which the nip width between the fixing roller 21 and the pressure roller 24 is small and the second pressure position is reached. In this case, since the tension of the pressure lever 26 by the spring 31 is large, the high pressure mode in which the nip width between the fixing roller 21 and the pressure roller 24 is large is set.
[0018]
As described above, in the fixing operation in the first embodiment of the present invention, the fixing roller 21 is heated by the heat source 22 after the power supply (not shown) is turned on as shown in FIGS. The process is started when the temperature detected by the temperature detecting means 23 reaches the fixable temperature. After the start of the operation, as shown in FIG. 5, the heat source 22 is turned off for a fixed time (Δt = t ₂ −t ₁ ) during continuous feeding of the transfer paper. During this time, the heat supply by the heat source 22 is lost, so that the heat is supplied to the transfer paper only by the heat accumulation of the fixing roller 21. Therefore, the temperature drop (ΔT = T ₂ −T ₁ ) of the fixing roller 21 varies depending on the difference in the width of the nip portion that holds the transfer paper between the fixing roller 21 and the pressure roller 24, that is, the difference in the applied pressure.
[0019]
In such a case, the control means not shown in the drawing includes an intermediate nip width X _M between the nip width X _{L in the} low pressure mode and the nip width X _{H in} the high pressure mode / (X _L + X _H ) / If the temperature change (temperature gradient: A _M = ΔT _M / Δt) due to the temperature drop ΔT _M for a certain time Δt in 2 is set, and the temperature gradient A during actual paper feeding is A <A _M , the low pressure mode is determined. , it is determined that a ≧ a _M if the high pressure mode, heat control means has on the transfer sheet to adjust the heat supplied by the heat source 22 such that the top qs.
[0020]
Next, as shown in FIGS. 9, 10, and 11, the fixing operation in the second embodiment of the present invention is performed in the same manner as described above, with the temperature T of the intermediate nip width X _M after a predetermined time Δt after the heat source 22 is turned off. _{If M} is set and the temperature T during actual paper passing is T> T _M , the low pressure mode is determined. If T ≦ T _M , the high pressure mode is determined. The amount of heat supplied by the heat source 22 is adjusted so that
[0021]
Next, in the fixing operation in the third embodiment of the present invention, as shown in FIGS. 12, 13, and 14, the width of the nip portion between the fixing roller 21 and the pressure roller 24 is made constant, and plain paper (basis weight is about 70 g). / m ² ), a temperature change (temperature gradient: A _N = ΔT _N / Δt) due to a temperature drop ΔT _N for a certain time Δt is set, and if the temperature gradient A during actual paper feeding is A <A _N The transfer sheet is judged to be thin, and if A ≧ A _N , the transfer sheet is judged to be thick, and the amount of heat supplied by the heat source 22 is adjusted so that the amount of heat given to the transfer sheet by the control means becomes the optimum amount. .
[0022]
Next, in the fixing operation in the fourth embodiment of the present invention, as shown in FIGS. 15, 16, and 17, plain paper (basis weight of about 70 g / m) after a predetermined time Δt after the heat source 22 is turned off as described above. ²⁾ set the temperature T _n, if the temperature T is T> T _n at the time of a real paper passing, it is determined that thin rolling transfer paper that is fed, determines the cardboard a T ≦ T _n if the transfer sheet Then, the amount of heat supplied by the heat source 22 is adjusted so that the amount of heat given to the transfer paper by the control means becomes an optimum amount.
[0023]
Next, in the fixing operation in the fifth embodiment of the present invention, as shown in FIGS. 18, 19, and 20, the leading edge of the first transfer sheet fed in the same manner as described above is added to the fixing roller 21. The time required for the detected tip to reach the nip is detected by the tip detection member 40 provided upstream from the nip with the pressure roller 24 by a distance _L, and the arrival time t _L is determined by the conveyance speed. Therefore, as shown in FIG. 19, the heat source 22 is turned off for a fixed time (Δt = t ₂ −t ₁ ) after the time t _L when the front end reaches the nip portion after the front end detection member 40 detects the front end. During this time, the heat supply by the heat source 22 is lost, so that the heat is supplied to the transfer paper only by the heat accumulation of the fixing roller 21.
[0024]
Therefore, the temperature drop (ΔT = T ₂ −T ₁ ) of the fixing roller 21 varies depending on the difference in the width of the nip portion that holds the transfer paper 10 between the fixing roller 21 and the pressure roller 24, that is, the difference in the applied pressure. As in the first embodiment, as shown in FIGS. 6, 7 and 8, first, the nip width X _M between the nip width X _{L in the} low pressure mode and the nip width X _{H in the} high pressure mode = ( Set temperature change (temperature gradient: A _M = ΔT _M / Δt) due to temperature drop ΔT _M for a certain time Δt at X _L + X _H ) / 2, and if the temperature gradient A during actual paper feeding is A <A _M if, it is determined that the low pressure mode, it is determined that a ≧ a _M if the high pressure mode, the control means adjusts the heat supplied by the heat source 22 so that the amount of heat applied to the transfer sheet becomes the optimum amount.
[0025]
Further, in the fixing operation in the sixth embodiment of the present invention, as shown in FIGS. 21 and 22, the absolute value ΔT ′ of the temperature of the fixing roller 21 that has changed during a predetermined time Δt ′ during continuous passage of the transfer paper 10. Is smaller than the allowable change temperature ΔT _A (ΔT ′ <ΔT _A ), the heat source 22 is turned off for a fixed time (Δt = t ₂ −t ₁ ). During this time, the heat supply by the heat source 22 is lost, so that the heat is supplied to the transfer paper only by the heat accumulation of the fixing roller 21.
[0026]
Accordingly, the temperature drop (ΔT = T ₂ −T ₁ ) of the fixing roller 21 varies depending on the difference in the width of the nip portion that holds the transfer paper between the fixing roller 21 and the pressure roller 24, that is, the difference in the applied pressure. As in the first embodiment, as shown in FIGS. 6, 7 and 8, first, the nip width X _M between the nip width X _{L in the} low pressure mode and the nip width X _{H in the} high pressure mode = ( Set temperature change (temperature gradient: A _M = ΔT _M / Δt) due to temperature drop ΔT _M for a certain time Δt at X _L + X _H ) / 2, and if temperature gradient A during actual paper feeding is A <A _M , it is determined that the low pressure mode, it is determined that a ≧ a _M if the high pressure mode, the control means adjusts the heat supplied by the heat source 22 so that the amount of heat applied to the transfer sheet becomes the optimum amount.
[0027]
【The invention's effect】
The present invention is as described above, and includes a fixing roller having a heat source and a pressure roller pressed against the fixing roller, and the pressing force of the pressure roller is switched to a plurality of types, and the surface temperature of the fixing roller is adjusted. In the fixing device having the temperature detecting member to detect, the invention according to claim 1 is a low-pressure mode in which the nip width between the fixing roller and the pressure roller is small, and a high-pressure mode in which the nip width between the fixing roller and the pressure roller is large. And a fixed time Δt at a nip width X _M (X _M = (X _L + X _H ) / 2) between the nip width X _{L in the} low pressure mode and the nip width X _{H in the} high pressure mode. The temperature gradient A _M (A _M = ΔT _M / Δt) due to the temperature drop ΔT _M is set, and the heat source is turned off for a certain period of time while the transfer paper is continuously fed, and the temperature detection member detects Fixing roller Calculating a temperature gradient A during actual paper feed based on the temperature change of the surface temperature, if the temperature gradient A is A <A _M, determines that the low pressure mode, it is determined that A ≧ A _M if high pressure mode, Since there is a control means for controlling the amount of heat supplied by the heat source so that the amount of heat given to the transfer paper is the optimum amount, the difference in the nip width between the fixing roller and the pressure roller and the type of transfer paper The amount of heat applied to the transfer paper can be adjusted to the optimum amount in response to the difference, and the fixing quality can be improved.
[0028]
Similarly, the invention of claim 2 includes a low pressure mode in which the nip width between the fixing roller and the pressure roller is small, and a high pressure mode in which the nip width between the fixing roller and the pressure roller is large, and the nip in the low pressure mode. width _{X L} and the intermediate nip width _X M and the nip width _{X H} when the high pressure mode _{(X M = (X L +} X H) / 2) temperature gradient due to the temperature drop [Delta] T _M for a predetermined time Δt in _a M (a _M = ΔT _M / Δt), and the surface of the fixing roller is detected by detecting the temperature detecting member during a certain period of time while the first transfer sheet passes through the fixing device and the heat source is turned off for a certain period of time. calculating a temperature gradient a during actual sheet passing on the basis of the temperature change, if the temperature gradient a is a <a _M, determines that the low pressure mode, it is determined that a ≧ a _M if the high pressure mode, the transfer sheet So that the amount of heat given to the It is provided with the control means for adjusting the heat supplied by the sources, corresponding precisely to the difference in width of the nip portion and the transfer sheet type of difference between the fixing roller and the pressure roller, giving the transfer paper The amount of heat can be set to an optimum amount in a short time, and the fixing quality can be improved efficiently.
[0029]
Similarly, the invention of claim 3 includes a low pressure mode in which the nip width between the fixing roller and the pressure roller is small, and a high pressure mode in which the nip width between the fixing roller and the pressure roller is large, and the nip in the low pressure mode. width _{X L} and the intermediate nip width _X M and the nip width _{X H} when the high pressure mode _{(X M = (X L +} X H) / 2) temperature gradient due to the temperature drop [Delta] T _M for a predetermined time Δt in _a M (a _M = ΔT _M / Δt) is set , and the heat source is turned off for a predetermined time in a state where the temperature of the fixing roller is stable, and based on the temperature change of the surface temperature of the fixing roller by the detection of the temperature detecting member during that time calculating a temperature gradient a in actual sheet passing, if the temperature gradient a is a <a _M, determines that the low pressure mode, it is determined that a ≧ a _M if the high pressure mode, the amount of heat applied to the transfer sheet optimum To the heat source so that the amount That it is provided with the control means for adjusting the supply amount of heat, and respond appropriately to the differences and the transfer paper types differences of the width of the nip portion between the fixing roller and the pressure roller, stable transfer paper The amount of heat applied to the toner can be set to an optimum amount, and the improvement in fixing quality can be realized stably.
[Brief description of the drawings]
FIG. 1 is a schematic front view of a typical image forming apparatus provided with the present invention.
FIG. 2 is a perspective view of a main part of the present invention.
FIG. 3 is a state diagram in a low pressure mode of a pressure switching member of the pressure roller.
FIG. 4 is a state diagram of the same member in a high pressure mode.
FIG. 5 is an initial operation time chart of the first embodiment of the present invention.
FIG. 6 is an operation time chart of the above.
FIG. 7 is a correlation diagram between the sheet passing size and the intermediate nip width.
FIG. 8 is a flowchart of the above.
FIG. 9 is an operation time chart of the second embodiment of the present invention.
FIG. 10 is a correlation diagram between the sheet passing size and the intermediate nip width.
FIG. 11 is a flowchart of the above.
FIG. 12 is an operation time chart of the third embodiment of the present invention.
FIG. 13 is a correlation diagram between the sheet passing size and the intermediate nip width.
FIG. 14 is a flowchart of the above.
FIG. 15 is an operation time chart of the fourth embodiment of the present invention.
FIG. 16 is a correlation diagram between the sheet passing size and the intermediate nip width.
FIG. 17 is a flowchart of the above.
FIG. 18 is a schematic configuration diagram of a fifth embodiment of the present invention.
FIG. 19 is a time chart of the above.
FIG. 20 is a flowchart of the above.
FIG. 21 is a time chart according to the sixth embodiment of the present invention.
FIG. 22 is a flowchart of the above.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 1st charging device 2 photoreceptor 3 1st image exposure 4 1st developing device 5 2nd developing device 6 2nd image exposure 7 Bias roller 8 Voltage application means 9 Transfer belt 10 Transfer paper
11 Solenoid 12 Spring
13 Second charger 21 Fixing roller
22 Heat source 23 Temperature detection means
24 Pressure roller 25 Bearing
26 Pressure lever 27 Axis
28 Support shaft 29 Support pin
30 Long hole 31 Spring
32 Vertical movement member 33 Side plate
34 Rotating shaft 35 Gear
36 cam 37 overhang
40 Tip detection member

Claims (4)

In a fixing device having a fixing roller having a heat source and a pressure roller pressed against the fixing roller, and having a temperature detection member that detects the surface temperature of the fixing roller by switching the pressing force of the pressure roller to a plurality of types ,
Fixing roller and the lower pressure nip width is small mode the pressure roller, the nip width of the fixing roller and the pressure roller is large and the high-pressure mode is set, and when the nip width X _L and the high pressure mode when the low-pressure mode nip width _{X H} intermediate nip width _X M of _{(X M = (X L +} X H) / 2) temperature gradient _a M due to the temperature drop [Delta] T _M for a predetermined time Delta] t in _{(a M = ΔT M / Δt} ) is Is set,
During the continuous feeding of the transfer paper, the heat source is turned off for a certain period of time, and a temperature gradient A during actual paper feeding is calculated based on the temperature change of the surface temperature of the fixing roller detected by the temperature detecting member during this time. If a is a <a _M, determines that the low pressure mode, it is determined that a ≧ a _M if the high pressure mode, as the amount of heat applied to the transfer sheet to adjust the heat supplied by the heat source so that the optimum amount A fixing device comprising a control means for controlling. In a fixing device having a fixing roller having a heat source and a pressure roller pressed against the fixing roller, and having a temperature detection member that detects the surface temperature of the fixing roller by switching the pressing force of the pressure roller to a plurality of types ,
Fixing roller and the lower pressure nip width is small mode the pressure roller, the nip width of the fixing roller and the pressure roller is large and the high-pressure mode is set, and when the nip width X _L and the high pressure mode when the low-pressure mode nip width _{X H} intermediate nip width _X M of _{(X M = (X L +} X H) / 2) temperature gradient _a M due to the temperature drop [Delta] T _M for a predetermined time Delta] t in _{(a M = ΔT M / Δt} ) is Is set,
While the first transfer paper passes through the fixing device, the heat source is turned off for a predetermined time , and the temperature gradient A during actual paper feeding is based on the temperature change of the surface temperature of the fixing roller detected by the temperature detecting member during that time. calculates, if the temperature gradient a is a <a _M, determines that the low pressure mode, it is determined that a ≧ a _M if the high pressure mode, according to the heat source as heat applied to the transfer sheet is the optimum amount A fixing device comprising control means for controlling the amount of heat supplied . In a fixing device having a fixing roller having a heat source and a pressure roller pressed against the fixing roller, and having a temperature detection member that detects the surface temperature of the fixing roller by switching the pressing force of the pressure roller to a plurality of types ,
Fixing roller and the lower pressure nip width is small mode the pressure roller, the nip width of the fixing roller and the pressure roller is large and the high-pressure mode is set, and when the nip width X _L and the high pressure mode when the low-pressure mode nip width _{X H} intermediate nip width _X M of _{(X M = (X L +} X H) / 2) temperature gradient _a M due to the temperature drop [Delta] T _M for a predetermined time Delta] t in _{(a M = ΔT M / Δt} ) is Is set,
While the temperature of the fixing roller is stable, the heat source is turned off for a certain period of time, and a temperature gradient A during actual paper feeding is calculated based on the temperature change of the surface temperature of the fixing roller detected by the temperature detection member during this time. If the temperature gradient a is a <a _M, determines that the low pressure mode, it is determined that a ≧ a _M if the high pressure mode, the amount of heat applied to the transfer sheet to adjust the heat supplied by the heat source so that the optimum amount A fixing device comprising control means for controlling as described above .   4. The fixing device according to claim 1, wherein the heat source is turned off non-forcefully.

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